Reciever, frequency deviation measuring unit and positioning and ranging system
In a system for measuring a time difference of arrival of signals for positioning, an accurate time difference is measured by a receiver which is reduced in power consumption, size, and cost. The system comprises a node (under measurement) for transmitting a positioning signal, a reference station for transmitting a reference signal, and a plurality of access points for receiving the positioning signal and reference signal, and a server connected to the plurality of access points through a network. Each of the plurality of access points measures a time difference between the reception of the positioning signal and the reception of the reference signal, and a frequency deviation from the reference station, using a clock signal and a signal for shifting the clock signal, and the server calculates the position of the node based on the measured time difference and frequency deviation.
1. A positioning system, comprising:
a node which transmits a first transmission signal;
a reference station which transmits a second transmission signal after receiving the first transmission signal transmitted by the node;
a plurality of access points each of which includes;
a reception unit which receives the first transmission signal and the second transmission signal;
an A/D conversion unit which includes an A/D converter for converting the first transmission signal and the second transmission signal from an analog form to a digital form and a sampling clock generator unit for generating sampling clocks determining timings at which the A/D converter performs analog-to-digital conversion;
a sampling timing control unit which outputs control signals for shifting a phase of the sampling clocks;
a synchronization trap unit which matches phases of the first transmission signal and the second transmission signal with the phase of the sampling clocks by using the control signals;
a synchronization tracking unit which adjusts the phase of the sampling clocks to maintain synchronization of the first transmission signal and the second transmission signal;
a time difference measurement unit which counts respective numbers of the sampling clocks and the control signals, and measures a reception time difference between the first transmission signal and the second transmission signal using the counted numbers of the sampling clocks and the control signals; and
a frequency deviation measuring unit which counts respective numbers of the sampling clocks and the control signals, and measures a frequency deviation of a clock between a transmitter and the access point using the counted numbers of the sampling clocks and the control signals;
a server which calculates the position of the node using the reception time difference corrected based on the frequency deviation.
2. The positioning system according to claim 1 , wherein the transmitter is the reference station or the node.
3. The positioning system according to claim 1 , wherein each of the first transmission signal and the second transmission signal is a signal of an ultra-wide band communication scheme.
4. The positioning system according to claim 3 , wherein each of the first transmission signal and the second transmission signal is a signal composed of a sequence of directly spread impulses.
5. A ranging system comprising:
a first communication device which transmits a first transmission signal; and
a second communication device which transmits a second transmission signal to the first communication device after receiving the first transmission signal transmitted by the first communication device,
wherein the first communication device includes:
an A/D conversion unit which includes an A/D converter for converting the second transmission signal from an analog form to a digital form and a sampling clock generator unit for generating sampling clocks determining timings at which the A/D converter performs analog-to-digital conversion;
a sampling timing control unit which outputs control signals for shifting a phase of the sampling clocks;
a synchronization trap unit which matches the phase of the second transmission signal with the phase of the sampling clocks by using the control signals;
a synchronization tracking unit which adjusts the phase of the sampling clocks to maintain synchronization of the second transmission signal;
a time difference measurement unit which counts respective numbers of the sampling clocks and the control signals, and measures a time difference from the transmission of the first transmission signal to the reception of the second transmission signal using the counted numbers of the sampling clocks and the control signals;
a frequency deviation measuring unit which counts respective numbers of the sampling clocks and the control signals, and measures a frequency deviation of a clock between the first communication device and the second communication device using the counted numbers of the sampling clocks and the control signals; and
a calculation unit which calculates a distance between the first communication device and the second communication device using the time difference corrected based on the frequency deviation.
6. The ranging system according to claim 5 , wherein each of the first transmission signal and the second transmission signal is a signal of an ultra-wide band communication scheme.
7. The ranging system according to claim 6 , wherein each of the first transmission signal and the second transmission signal is a signal composed of a sequence of directly spread impulses.
8. A receiver comprising:
a reception unit which receives a transmission signal from a transmitter;
an A/D conversion unit which includes an A/D converter for converting the transmission signal from an analog form to a digital form and a sampling clock generator unit for generating sampling clocks determining timings at which the A/D converter performs analog-to-digital conversion;
a sampling timing control unit which outputs control signals for shifting a phase of the sampling clocks;
a synchronization tracking unit which adjusts the phase of the sampling clocks to maintain synchronization of the transmission signal; and
a frequency deviation measuring unit which counts respective numbers of the sampling clocks and the control signals, and measures a frequency deviation of a clock between the transmitter and the receiver using the counted numbers of the sampling clocks and the control signals.
9. The receiver according to claim 8 , further comprising:
a synchronization trap unit which matches phases of the transmission signal with the phase of the sampling clocks by using the control signals.
10. The receiver according to claim 9 , further comprising:
a time difference measurement unit which counts respective numbers of the sampling clocks and the control signals, and measures a time difference from the transmission of a signal to the reception of the transmission signal transmitted by the transmitter using the counted numbers of the sampling clocks and the control signals.
11. The receiver according to claim 8 , wherein the transmission signal is a signal of an ultra-wide band communication scheme.
12. The receiver according to claim 11 , wherein the transmission signal is a signal composed of a sequence of directly spread impulses.